1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus for recording an information on an information recording medium such as an optical disk or reproducing a recorded information therefrom. In particular, the present invention relates to a drive control of a spindle motor.
2. Related Background Art
Hitherto, there is known an optical disk on which a wobble for generating a clock is formed, and rotational control of a spindle motor with a wobble reproduced signal of a disk is described in, for example, Japanese Patent Application Laid-Open No. H07-311962.
Further, the rotational control of a spindle motor using a frequency generator (FG) means signal is generally performed as described in, for example, Japanese Patent Application Laid-Open No. H11-176073.
Here, in a case of performing the rotational control of a spindle motor, there can be used an FG output for providing an FG signal having a frequency proportional to the rotation number of the spindle motor, or an output of a wobble phase locked loop (PLL) means for generating a clock which is synchronous with the wobble formed on the optical disk from a reproduced signal. At this time, the rotational control of a spindle motor can be performed based on an output of the FG means in a case where a wobble PLL is in an unlocked state, and based on an output of a rotation number detection means in a case where the wobble PLL is in a locked state.
In the optical disk having a plurality of recording layers, in a case where an optical head changes a layer for recording or reproducing, the wobble PLL is in an unlocked state since a wobble signal cannot be reproduced, which makes it necessary to perform the rotational control of a spindle motor with the output of the FG means. However, at this time, in a case where there is an error in setting a desired FG frequency value for performing the rotational control of a spindle motor, there is posed the problem that the rotation of a spindle motor becomes unstable, and an excessive power is required for changing the rotation number.